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American Deputy Beard Mackie Indicator | AMERICAN DEPUTY - American Deputy safety lamp with Beard-Mackie sight indicator, aluminum and brass with brass bonnet, 10 3/4 in. tall to top of hook ring, 3 1/2 in. base dia., marked on base ring AMERICAN SAFETY LAMP & MINE SUPPLY CO. SCRANTON, PA and marked on bonnet AM. SAFETY LAMP & M. S. CO. SCRANTON, PA, ex-Henry Pohs collection (The Beard-Mackie sight indicator improved the ability of miners to determine the amount of methane present underground by observing the flame and glow on filaments in the flame cap. Invented by James T. Beard and Mathew D. Mackie, both of Scranton, it was first used in March 1903. Based on the fact that as methane levels in the atmosphere are increased, the flame burns hotter. The indicator includes 7 platinum filaments (the top six are looped) attached to a brass frame approximately 3/4 in wide and 3 1/2 in. tall that is situated above the wick tube of the lamp. The bottom straight standard wire is calibrated to glow in the flame cap in open air outside the mine. Each successive wire filament will glow in the mine atmosphere as the methane concentration increases by 1/2 percent until a glowing top filament would indicate a methane concentration of 3 percent. The glass globe is painted black to improve the readability of the indicator. See Steinberg, Mining Artifact Collector #1, pp 18-19) | Original Image |
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